Vents find use in many applications. For example, in the automotive industry, electrical component housings, gear housings, brake housings and even vehicle bodies use vents to equalize pressure between the housing or body interior and the surrounding environment. In other applications, the function of the vent is not bulk flow for pressure equalization, but diffusion for the purpose of transporting select components across the media, such as the diffusion of water across a media for moisture control. In these types of applications the driving force is not pressure, but temperature, concentration gradients, osmotic pressure, electrostatic attraction or repulsion, or some other driving force. Vents are also used in many other applications, such as electrical and mechanical equipment housings or chemical containers. Such housings, enclosures or containers are collectively referred to herein as a “housing.”
In many applications, vents must not only be gas permeable to allow for pressure equalization, but also be liquid impermeable to seal the interior of a housing from moisture, liquids or contaminants, which can damage internal equipment or components and corrode the housing.
Known adhesive vents contain a porous expanded PTFE (ePTFE) on a ring of a double sided pressure sensitive adhesive, one side of the adhesive is bonded to the ePTFE membrane and the other side to the housing.
Press fitted vents containing a molded polymer or plastic body and a porous membrane formed from polytetrafluoroethylene (PTFE), polypropylene or polyethylene are known. Known polymer vents are used as air vent devices in, for example, a breather valve, a filter, a diaphragm device, etc. Press-fitted vents typically include a membrane with circumferentially located holes that are positioned between rigid resin portions bound together through the circumferentially located holes. This rigid member is encompassed by a soft resin to form the press fitted article.
Many other configurations of molded polymer or plastic vents are known, however, all suffer significant shortcomings. Polymer or plastic vents and adhesive vents each lack durability as well as heat and chemical resistance. Accordingly, these vents cannot be used in certain applications where they may be subject to high temperatures (above 150° C.), ultraviolet (“UV”) or chemical degradation or impact. A shortcoming of a press-fitted vent is that they do not have a low profile.
Metal vents are known to provide improved durability in some applications. Also, some special plastic materials like epoxies or other thermoset plastics may provide durability. An integral vent containing such metal or specialty plastic materials bonded to a porous ePTFE membrane is desirable, yet heretofore unachievable.